Truing means for formed gear grinding wheels



March 14, 1933. I E LLER 1,900,943

TRUING MEANS FOR FORMED GEAR GRINDING WHEELS Filed Sept. 17, 1929 5 Sheets-Shet l March 14, 1933. E. w. MILLER TR UING MEANS FOR FORMED GEAR GRINDING WHEELS 5 Sheets-Sheet 2 Filed Sept. 17, 1929 s s f March 14, 1933. E. w. MILLVER TRUING MEANS FOR FORMED GEAR GRINDING WHEELS Filed Sept. 17, 1929 SSheets-Sheet s 7 C4, 3 H

' P252060 Mara-@15 2? E. W. MILLER S FOR FORMED GEAR GRINDING WHEELS TRUING MEAN March 14, 1933.

Filed Sept. 17, 1929 E. w. MILL-ER March 14,1933.

TRUING MEANS FOR FORMED GEAR GRINDING WHEELS Filed Sept. 17, 1929 5 Sheets-Sheet 5 jar/fez?? 22047 2 Patented Mar. 14, 1933 UNITED STATES.

PATENT mm:

EDWARD W. OF SPRINGFIELD, VERMONT, ASSIGNOR TO THE FELLOWS GEAR OOIPANY, OE SPRINGFIELD, VERMONT, A CORPORATION 01 VERHON'I TRUING MEANS FOR FORMED GEAR GRINDING WHEELS Application filed September 1'7, 1929. Serial No. 388,884.

This invention relates to the art of finishing ar teeth by grinding with the use of a grin d ing wheel having a formed grmdmg surface which imparts a complemental or counter art form to the faces of the gear teeth. t is primarily concerned with means for dressing the (grinding wheel to give its active face the sired form; and further concerned, among other things, with means associated with the foregoing for locating the formed face of the wheel in a given relation to the work. Gear finishin type above referred to havefiong been known, but those heretofore used for finishin volute gear teeth have been incapable o giving perfect satisfaction, due to ack of practical means for making a sufliciently true involute profile in the'grinding wheel face to finish involute gear teeth with the desired.

perfection of accuracy. Meshing gear teeth which are -not true within narrow limits of accuracy make an objectionable noise in runrun wheels for mac nes of the type indicate having rindin or active faces oftrue involute pro%le, an to provide a truing or dressing means capable of initially forming such profile, and maintaining it, with an exact and accurate involute curvature corresfonding to the involute from any desire base circle.- A further object has been to locate the active face on the wheel in a position such that it is rather a part of the riphery than of the end face of the wheel. n accomplishing these objects I have provided a truin apparatus in which the truing tool is cause to move in a path conformin to that ofa given point in an ine'xtensib e cord being.

wrap about or unwrapped from a cylindrica surface; and in the preferred embodiment of which the apparatus is mounted .on

the grinding machine so that .the path of the tool is in the prolongation of one of the tooth faces of the work piece. The invention consists in the means and combinations described in the following specification for carrying the foregoing objects into effect, together with equivalents thereof and the principles of means embodied therein and compremachines of the in- ...seen from the le It has been mfiobject to provide grindin hended within the scope of the following claims.

In, the drawings herewith, Fig. 1 is a front elevation of a gear-grindmg machine having my improved truing means in operative association with the grinding wheel; i r

2 is a plan view of the machine;

F 1g. 3 is a fragmentar longitudinal section taken on line 3-3. of ig. 2, and showing the work holding and indexing means of the machine;

Fig. 4 is a fra Fig. 6 is a longitudinal section of the tru-.

llllg means taken on line 6-6 of Fig. Land e arged; 4

Fig. 7 1s a fra on line 7-7 of l igs. 1 and 6 Fig. 8 is a view similar to Fig. 5 but showt e truing means in a different position; 1g}. 9 is a diagrammatic view illustrating the .c aracteristic princi les of the coacting entary endelevation as of Figs. 1 and 2 reprementary cross section taken elements which control t e movement of the I truing tool;

Fig. 10 is a cross section on'line 10-10 of i 11 is a fragmentary. elevation showing t e relationship of the work and grindmyiyheel when in operation;

v igs. 12 and 13 aredetail views of the truin tool holder and meansfor shifting and adJIPSting it. 7

, he machine comprises a basel on which is a slide 2 movable to right and left (with respect to Figs. land 2) on ways 3 (Fig. 4) being so moved by a crank .4 and a connectlngrod 5, shaft 6 and belt ulley 7, as may be plainly understood from t e drawings without further explanation. The-slide 2 carries an indexing head or fixture 8 and a su ort or fixture 9 for the truing mechanism. ese fixtures hold centers 10 and 11 by which is suppprted an arbor 12 having clamped thereon t e work piece 18, a ar which has been previously cut and of w ich the tooth, faces are to be finished by grinding. The center 10 in the indexing head 8 is secured in a liollow shaft 14 which is rotatable in the head and carries a crank 15 and index disk 16, the latter having a circular series of holes adapted to be engaged singly b a locking pin 17, as shown in Fig. 3, and aving lugs 18 engaging a dog 19 secured to the work carrying arbor 12.

. Rising from the machine base beside and above the slide 2 is a head 20 having bearings 21 in which is mounted a horizontal shaft carrying the grinding wheel 22 and a driving belt pulley 23. The grinding wheel overhangs the work carrying slide and is located off center with respect to the work, by which I mean that it is at one side of the vertical plane through the axis of the work, and of the supporting centers thereof. More broadly stated, the wheel is at one side of the plane which passes through the axis of the ,work and perpendicular to the axis of the wheel. This relat onship is shown in Figs. 4, 7 and 11. The grinding wheel is designed to act on only one side of one tooth at a time, and to that end has agrinding face or active surface 24 adjacent to its periphery and at the side of the latter away from the vertical plane through the work axis. In other words, the grinding wheel, instead of being radial to the work (in a plane containing the axis of the work) is in a plane at one side of and parallel to such axis, and its active face is at the side away from the parallel axial plane of the work. It is thus set over as far as it may be without causing interference with the adjacent side of the next tooth, in order that the character of grinding which it performs may approximate what-is called peripheral grinding rather than face grinding, and that the reaction of the grindmg thrust have as lar e a component radial to the wheel as possi le and the minimum possible component axially of the wheel. This arrangement. afl'ords greater wheel clearance, tends toward greater accuracy of grinding effect on the work, and gives a better control of the position and running of the wheel than is possible with a radially arranged wheel. V

In order to grind correctly the faces of involute gear teeth, the active face 24 of the grinding wheel must have a true involute curve in profile, that is, in planes radial to the wheel. In order to produce such curvature with.truth and accuracy, I have devised an attachment, carrying a truing tool of suitable character and having means fortraversing the point of such truing tool in a curved path, the curve of which is a true involute of the base circle of the gear being ground and is located in a radial plane of the wheel. Fig. 11 shows a work piece 13 having teeth r 25, the face curves 26 of which are involutes of the base circle 27 represented by broken likewise an involute of the same base circle.

The means for effecting the desired result are as follows.

The fixture 9 has two separated u rights 28 and 29 in which is fixed immovably the bar 11, the end of which provides the fixed center previously described. On the bar 11 between the uprights are fastened sleeves 30 and 31 having flanges at their remoter ends formed with external cylindrical surfaces 32 and 33 of the same, or approximately the same, diameter as the base circle of the ear being ground. Between these sleeves t ere is fixed on the bar a projection 34 having an involute face 35.

A rockable holder embraces the above named sleeves and projection and carries the truing tool. Said holder comprises a substantially cylindrical shell 36 and annular end plates or heads 37 and 38 secured to the ends of the shell, the latter being of such length that-the end plates, which overlap at their inner circumferences the flanges of sleeves 30 and 31, have a bearing on the outer end surfaces of such flanges to maintain the holder in position axially of the sleeves. Plates or bars 39 and 40 having straight and plane surfaces 41 and 42, respectively, are secured to the inner sides of the heads 37 and 38 and engage the cylindrical surfaces 32 and 33 respectively. The surfaces 41 and 42 are in the same plane- In one sideof the holder is an offset 43 providing a chamber in which is located a bar 44 mounted on a pivot 45 and having a projection 46 with a plane surface 47 overlapping the projection 34 and bearing on the curved surface 35 of the latter. Screws 48 and 49 are fitted in opposite walls of the offset 43 and bear on the bar 44 to adjust the latter angularly about its pivot. A cover 50 is secured over the end of the offset and carries a handle 51 by which the holder may be manually rocked. Limits to the rocking movement are set by a projection 52 on the holder located between fixed stops or abutments 53 and 54 on the base part of the head 9 and on the upright 38 thereof. The truin tool 55, which may be a diamond or the lie such as is commonly used for truin abrasive wheels, is set in the end of a shan 56 which in turn projects from the side of the terminal head 57 of a shaft 58 which is mounted to fit closely but rotatably in a sleeve 59 projecting in the axial direction from the head plate 38 of the holder. Said sleeve projects to such a distance as necessary to locate the truing tool in the same vertical plane with the axis of the grinding wheel when the slide 2 is in one of its possible sitions, and while the main portion of the older is volute rack an far enough away from the wheel to be clear of it. In other words, the arrangement is such that the truing tool may be placed where its arc of travel is in a radial plane of the wheel, so that it may form the profile of the active grinding face-in a radial'plane. Preferably the truing tool is caused to occupy this position when the carrier slide 2 is at one l mit of its travel, for instance, as shown in Fig 1, in order to facilitate correct placement of the tool.

' The point of the truing tool is located in the same plane with the surfaces 41 and 42, and may be fixed immovably in this plane, but preferably is arranged with capacity for independent rotation, as previously stated, for the purpose of accurate adjustment, and for another purpose, later explained. By virtue of its location in this plane, the rockingof the holder causes it to travel in an involute curve because the surfaces 41 and 42 then roll upon the cylindrical surfaces 32 and 33. i

The overlapping projections 34 and 46, and the means for ad usting the latter, are provided in order to prevent uncontrolledslip of the rocking holder on the cylinders 32,

33, and also to permit of variation, within limits, of the actual base circle with respect to which the path of the truin tool is developed. Owing to the steep inc ination of the plane surfaces 41 and 42, which results from the offset location of the grinding wheel it is possible to locate the projection 34 directly under the projection 46 and utilize gravity as the sole means for holding the coacting surfaces of these projections in engagement, which is of advantage from the standpoint of simplicity. These projections constitute in effect the matin teeth of a single toothed ingear couple, of which the lane established y the-surfaces 41 and 42 is the pitch plane. The plane face 47 of the rack tooth 46 may have any desired inclina tion, within practicable limits, to the pitch plane. The base circle for the involute face 35 of rojection 34 is determined according to well nown principles of involute gear design, as shown by the diagram in Fig. 9, thus: From the pitch point 60, which is the intersection between the pitch plane 42, the radius 61 of the work axis, perpendicular to such plane, and the face 47 of the rack tooth when the latter is in neutral position, a line 62 T is laid -outperpendicular to the rack tooth face. The circle 63 drawn tangent to the line 62 with the work axis as the center is the base circle with respect to which the involute curve 35 is developed. With the relationship existing as thus defined, rocking of the holder produces a rolling effect between the cylinders 32, 33 and plane surfaces 41,42, without slip,

and thetruing tool is caused to describe a curve which is a true and accurate involute of the cylinders 32 and 33. When the tool is thus moved in the perpendicular plane containing the axis of the grinding wheel, and

truing tool forms the active surface comple mental to the desired tooth form and in the location relative to the work axis which will cause the teeth of the work piece to be ground off true and accurately. I

Angular adjustment of the rack tooth by means of the screws 48 and 49 enables an accurate setting to be made in case after a trial grinding the pressure angle of thev ground gear tooth is ound to be incorrect. It also enables the truing tool to describe an involute to a base circle slightly larger -or smaller than the c linders 32 and 33, since a change in the inc ination of the rack tooth face 47 will cause the pitch point to lie elsewhere than in the pitch plane 42; that is, to one side or the'other of such pitch plane according to the direction in which theinclination is shifted. Then when the tool holder is rocked, it will be moved at a rate proportional to the greater or less distance of the new pitch point from the axis, with some incidental slippage of the surfaces 41 and 42 on the cylinders 32 and 33, butwith the result gear teeth are located within the base circle.

This condition is illustrated in Fig. 11. Although only thepart of the tooth face outside of the base circle is an active working face,

nevertheless it is desirable to grind the tooth inward substantiall to its root in order that no stock may be le t which might injure the points of mating teeth. Accordingly 'the grinding wheel extends approximately to the root circumference of the gear, and I have made the truing tool effective to dress the active face of the wheel beyond the limit of the involute curvature bymounting the tool rotatably in the holding sleeve 59 and by providing an outstanding arm or finger 64 adapted to be turned manually when the carrier has been rocked to the position where the truing tool is in the prolongation of the base cylinder, this location being determined by contact of the stops 52 and 53. The extended curvethen generated is the arc of a circle tangent to the involute curve and ex tending to the outermost edge of the active face. The character of this extended curvature is not important, provided only that thewheel is enabled to continue the tooth face curves smoothly to the tooth root.

A stop finger protrudes from the supporting sleeve beside the tool carrying head 57 to arrest the arm 64 at the limit of its forward movement. Another arm or bracket 66 rojecting from the sleeve carries an adustable stop screw 67 which enga es the arm 64 and arrests it when the truing tool is brought into the plane of surfaces 41, 42, or other pitch plane established by adjustment of the rack tooth face 47, previously described.

It will be readily understood that the operation of the machine carries the work piece back and forth across the formed face of the grinding wheel, which latter ives the prescribed shape to the tooth. A ter each tooth has been round, the workis indexed; and when all ave been ground on one side the work iece is removed from the arbor and replace in reverse position.

From time to time,'as often as desired, and when the work carriage is in the proper position, the truing tool is rocked to restore the grinding wheel face to true form. It may be understood without detailed explanation that adjusting means of a character well known in grinding machines may be provided in this machine for adjusting the wheel either in the axial direction, or vertically, or in both directions to maintain its active face in the correct workng position after repeated grinding and truing actions.

The relation of the truing means to the work holding means, by virtue of which the tool holder is rocked about the axis of the work piece and the tool itself caused to generate an involute to the base circle of the work in the exact location occupied by the tooth face next to be ground, is an important factor in insuring accuracy of result. It also enables a depth feed or increased cut to be made by shifting the work piece circumferentially through a small angle. However, although I claim all novelty and advantage in this feature, my invention is not specifically limited thereto, but includes all novel features in the truing fixture itself independently of its association with the work holding and carryin means of the machine. A truing fixture su stantially like that here described may be used apart from a gear grinding machine, for the purposes and in themanner described, with satisfaction as to results, although without the same ease and simplicity as in an association such as here illustrated.

It will be understood also that the same principles may be embodied in other constructions and arrangements of a machine and its parts than that here illustrated. For instance, the steep inclination of the rolling plane 41 -42 here shown is important only as a means for effecting the desired ofl center formation of the grinding n heel. If

it is preferred to arrange the wheel more nearly, or exactly, in a radial lane of the work, the rocking holder may e placed so that its planes are more nearly horizontal, and the rojection 34 correspondingly relocated. hese principles may be applied to a completely automatic machine in which the indexing of the work and the rocking of the truing means are performed automatically. I have shown here only provisions for manually performing these functions in the interest of simplicity and clearness, and because the new principles of the invention are thus adequately disclosed.

What I claim and desire to secure by Letters Patent is:

1. In a gear grinding machine, the combination with a work supporting center, of a cylinder coaxial with said center having an external surface substantially the same in diameter as the base circle of the prescribed involute curve of the gear tooth faces to be ground, a rockable holder having a plane surface engaging said cylindrical surface and adapted to rock thereon, a truing tool carried by said holder and located in the same plane with said plane surface, and overlapping projections, one of which is fixed with respect to said cylinder and the other is secured to the rocking holder, said projections having engaging surfaces formed correspondlngly to the mating tooth surfaces of a rack and gear couple of which the pitch line coincides with said plane surface.

2. A truing mechanism for forming an involute profile in a grinding wheel comprisin a stationar support having an exterior cy indrical sur ace, a rockable holder having a plane surface bearing on said cylindrical surface, a truing tool carried by said holder 4 and located in the same plane with said plane surface, a stationary projection having an involute curved surface crossing said cylindrical surface, and a coacting projection carried by said holder and having a plane face crossin the first named lane surface, the faces 0 said rojections being in contact with one anot er and having the same relation as the mating faces of an involute gear and rack couple of which the pitch line goincides with the first named plane surace. 3. A truing mechanism for forming an involute profile in a grinding wheei comprisin a stationar support having an exterior cy indrical sur ace, a rockable holder having a plane surface bearing on said cylindrical surface, a truing tool carried by said holder and located in the same plane with said plane surface, a stationarv projection having an involute curved sur ace crossing said cylindrical surface, a coacting projection carried by said holder and having a plane face crossing the first named plane surface, the faces of said projections being in contact with one another and having the same relation as the matin faces of an involute gear and rack couple o whichthe pitch line coincides with the first named plane surface, and means for adjusting the last named projection so as to alter the angle which its plane face makes with the first named plane surface, whereby to shift the location of the actual pitch line of the projections.

4. A grinding wheel truing mechanism comprising a relatively stationary support including a convex cylindrical surface and a projection having a curved face crossing the said surface, said curved face being an involute to a base clrcle concentric with said cylindrical surface, a rockable holder having a plane surface contacting and bearing on said cylindrical surface and. adapted to rock thereon, a projection pivoted on said holder having a plane face crossing the plane of the before named plane surface and adapted to bear on the curved face of the first projection, means for adjusting said projection about its axis to vary the angle which its face makes with said plane surface, and a truing tool carried by said holder in the same plane with the before named plane surface.

5. A truing mechanism for forming an involnte profile in a grinding wheel comprising a rockable tool holder having a plane contact surface, a cylindrical supporting surface with which said plane surface has rocking engagement, coacting involute rack and pinion teeth, the rack tooth of which iscarried by said holder and the pinion tooth secured to said support, andthe pitch line of which teeth substantially coincides with the plane of said plane surface, and means for adjusting the rack tooth angularly about an axis parallel to the axis of said cylindrical surface, whereby to shift the pitch line of said teeth to either side away from and toward the said plane.

In testimony whereof I have afiixed my EDWARD W. LHLLER.

no signature. 

